Green computing has been defined as the study and practice of using computing resources efficiently. Typically, technological systems or computing products that incorporate green computing principles take into account economic viability, social responsibility and environmental impact. In particular, green computing includes efforts to obtain maximized energy efficiency from the computer resources being used. Green computing is also described as the science behind efficient computing and performing tasks on a smaller power budget. All computer usage consumes energy, and depending on the energy source, such usage may also increase greenhouse gas emissions. The United States Government, as well as the information technology industry, recognizes the importance of efficient computing in order to reduce greenhouse gas emissions resulting from energy or power consumption. Large government and commercial initiatives are underway to identify environmentally conscious information technology programs and the most efficient computers.
Computer systems may impose a large burden on a power grid, and some estimate that the energy cost to run a large computer system may exceed the cost of the system hardware over its useful life. Energy is consumed by the system computational components, as well as to cool the environment and to provide illumination for operators. To reduce energy usage, manufacturers have developed numerous power-efficient technologies: for example, processor speeds and/or use can be adaptively reduced or stopped when the processor is not heavily used, monitors and peripherals can be put in a reduced power-consumption mode, etc. However, such mechanisms are configured to operate only on a localized level, in response to local considerations, for example manually triggered by a conscientious (or utility bill-paying) user or automatically by a hardware configuration or a software application running on the system (e.g., triggering a standby state after a given idle time, or in response to a heat monitor detecting a rise in an internal temperature associated with a powered computer component). Total energy or environmental savings realized by such processes may be nullified or insignificant when considered on an overall (e.g. annual) basis when energy used by the device in more-active or higher-powered uses is acquired during peak energy demand times, thus utilizing the highest-cost or most environmentally-degrading energy available to the device.